GC/MS CONFIRMATION OF ETHYLENE DIBROMIDE RESIDUE IN FOODS

Electron impact (EI) and negative ion chemical ionization (NICI) selected-ion-monitoring (SIM) GC/MS techniques are described for the confirmation of ethylene dibromide (EDB) residues in various food products.     

DETERMINANTS OF WORK ATTITUDES AMONG NEGROES.

THE MOTIVATOR-HYGIENE THEORY OF WORK ATTITUDES ASSUMES THAT 2 INDEPENDENT SETS OF VARIABLES DETERMINE JOB SATISFACTION AND DISSATISFACTION. THE GENERALITY OF THIS THEORY WAS TESTED WITH RESPONSES FROM 85 NEGRO BLUE-COLLAR WORKERS TO A 40-ITEM QUESTIONNAIRE. THESE DATA WERE FACTOR ANALYZED AND COMPARED WITH COMPARABLE DATA FROM 117 WHITE BLUE-COLLAR WORKERS. THE 2 SETS OF DATA APPEARED TO DIFFER ALTHOUGH SOME SIMILARITIES WERE FOUND. IT APPEARED THAT HYGIENE FACTORS WERE MORE IMPORTANT TO THE NEGROES THAN TO THE WHITES. THE 2-FACTOR THEORY MAY BE TOO SIMPLE TO ENCOMPASS THE CONCEPTS OF JOB SATISFACTION AND DISSATISFACTION, AT LEAST IN THE BLUE-COLLAR NEGRO. IT MAY BE THAT THE 2-FACTOR THEORY IS LESS USEFUL WHEN LOW-STATUS WORK IS CONSIDERED. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Particle Residence Time Distributions in Two-phase Flow in Straight Round Conduit

Residence times were studied for single particles (polystyrene spheres 19.1 mm diam) in the straight portion of the holding section of a continuous flow system. Particle residence times were all less than the mean residence time of fluid; their ranges were within particle-to-fluid residence time ratios of 0.8 to 1.0. The velocities of the fastest moving particles were all about 1.25 times the mean fluid velocity in the turbulent flow regime. Particle density was important in the flow patterns of two-phase flow. The effect of particle-to-fluid density ratios on the particle residence time followed a quadratic function where particles with density ratio of 1.01 had the least residence time.     

Closed Loop Optimization of Fixed Configuration Systems†

For the majority of all dynamic systems open loop optimal control generally results from optimization theory whereas a closed loop control is normally desired. By accepting a degradation in performance a closed loop control termed ‘ specific optimal control ’ can be obtained. A series of experiments were performed investigating this type of sub-optimal control. It was found that although the proper choice of the control parameter leads to easily implemented closed loop controls, there are major drawbacks to its use. The coefficients in the control law ore highly dependent upon the final time T, the system parameters, and the initial state of the system. Furthermore, the performance of the system was found to be a function of the algebraic form chosen for the control law. To determine the most optimum control law entails performing a series of computer experiments. This last difficulty may be circumvented in part by embedding the specific optimal control problem in an identification problem. Results of the experiments in this research indicate that this procedure is feasible.     

Sucrose Polyester Content in Foods by a Calorimetric Method

Lipids were extracted from the food sample with petroleum ether and sucrose polyesters (SPE) and triglycerides in the extract were hydrolyzed with 1N methanolic KOH for 8 min. Free sucrose was extracted with water, and quantified calorimetrically using a phenol-sulfuric acid test. Results were compared to a standard curve from known quantities of hydrolyzed SPE. Standard curves were linear and reproducible through 90% SPE (r = 0.999).     

AN APPROXIMATELY MINIMUM VARIANCE JACKKNIFE

Jackknifing is a nonparametric method of reducing bias in estimation procedures. The reduced-bias jackknife estimate is not, in general, a minimum variance (MV)estimate. The generalized jackknife is extended to allow the computation of jackknife estimates that are reduced in variance as compared with the usual jackknife estimate. The extended method is applicable in situations where there is information available on the covariance function of the given data set. This improved estimation procedure will then produce an approximately MV, reduced-bias estimate for any nonlinear function of the data. For linear combinations of the data, it is shown that the estimator reduces, as a special case, to an exactly MV, unbiased estimator.     

TEXTURE PROPERTIES OF GELLAN GELS AS AFFECTED BY TEMPERATURE

Gellan gels can be made very brittle, similar to agar gels, or very flexible, like gelatin gels. The entropy or enthalpy nature governing those gellan gel behaviors was studied by mechanical testing at temperatures varying from 2 to 62C. Both failure stress and strain for 1% low acyl and low acyl/high acyl mixed gellan gels decreased with increasing temperature, indicating that the hydrogen bonding contributed significantly to the stabilization of gellan gels in addition to the polyanion-calcium-polyanion bonding. Hydrophobic interactions were less important. The initial Young's modulus for two mixed high and low acyl gellan gels containing 2 mM Ca⁺⁺ increased with temperature from 2–42C, indicating entropy elasticity. Average molecular weight between adjacent crosslinks for these two mixed gels was larger than 10⁴. For other gels, the entropy elasticity was not a dominant mechanism for elastic force because of molecular weights between crosslinks and from the observation of negative temperature dependence of the modulus.